Active Vibration Cancellation in Sonic Well Logging Tools
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Solution Overview
Problem
Sonic well logging tools face noise interference from the tool housing and drill bit interactions, which complicates the acquisition of accurate formation parameters due to direct energy conduction and vibration-induced noise.
Innovation Solution
An acoustic logging tool with a collar featuring a primary acoustic source and a secondary canceling source, where the secondary source is strategically positioned to actively cancel collar vibrations, and computer simulations determine optimal canceling signals based on expected formation characteristics and drilling conditions to enhance signal processing and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a primary acoustic source is used to transmit sonic signals into the formation, then formation parameter measurement is enabled, but collar vibrations and noise interference are introduced
Solution Approach 1:
The patent applies active noise cancellation by using a secondary acoustic source to generate an anti-phase signal that destructively interferes with the collar vibrations and noise generated by the primary acoustic source. This converts the harmful vibrations into beneficial cancellation, allowing the useful sonic signals to be measured without the interfering noise
Solution Approach 2:
The secondary acoustic source is positioned and configured to preemptively counteract the collar vibrations before they propagate to the receivers. By generating the canceling signal in advance and positioning the secondary source strategically, the harmful vibrations are neutralized before they can interfere with the measurement process
2Object-affected harmful factors
If acoustic energy is transmitted at stop band frequency to reduce noise, then noise from drill bit interaction is reduced, but signal attenuation increases
Solution Approach 1:
The patent transmits acoustic energy at stop band frequencies, which are specifically chosen to minimize drill bit noise interference. Although this frequency selection causes increased signal attenuation, the active noise cancellation system compensates for these losses by providing a stable reference signal from the secondary source, enabling accurate formation parameter measurement despite the energy loss
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces noise-induced errors, allowing for clearer detection of formation properties like compressional and shear slownesses, improving the accuracy of sonic measurements and log generation.
Implementation Method 1
a second acoustic source on the collar, with the second acoustic source adapted to actively cancel collar vibrations introduced by the first acoustic source
Implementation Method 2
a sonic signal is transmitted from one longitudinal end of the tool and is received (detected) at the other end. The sonic signal from the transmitter enters the formation adjacent the borehole
Data Source
AI summary
An acoustic logging tool is provided with a first acoustic source that generates an acoustic signal primarily directed into the formation, the acoustic signal including a noise signal carried axially along the tool, a second acoustic source adapted to generate a noise canceling signal along the tool that actively and significantly cancels the noise signal, and a plurality of acoustic sensors axially spaced from each other along the tool and spaced from the first acoustic source and the second acoustic source. The acoustic sensors receive and record indications of pressure signals resulting from the acoustic signal and the noise canceling signal. The pressure signal indications may be processed in order to generate information regarding the formation.